Sydneysiders could have been forgiven for not knowing where they were this morning after the iconic skyline was shrouded in thick smoke and fog.
Tops of high-rise buildings, electricity towers and even the city's tallest building, Sydney Tower, have been hard to spot.
The conditions are being seen not only in the CBD, but across eastern NSW too, according to the Bureau of Meteorology.
The town of Camden, south-west of Sydney, and also Richmond, on the banks of the Hawkesbury, are experiencing the thickest fog, duty forecaster Jiwon Park said.
The blanket of fog is the result of hazard reduction burning in western Sydney and the Blue Mountains region.
The dust particles from the burn enhance the condensation process and those water droplets then stick to the particles.
"And if they form large droplets they become fog droplets," Mr Park said.
"If it doesn't become fog it at least becomes a haze.
"We expect conditions to improve during the later part of the morning."
Sydney Airport is experiencing reduced visibility, the BOM said, but there are currently no flight delays.
Hazard reduction burns are an important part of preparing for bushfires, but the NSW Rural Fire Service advises those who are likely to experience problems relating to smoke to reduce outdoor activities.
Mr Park said the conditions over the next couple of days would be less favourable to fog due to southerly winds and coastal showers.ABC